How to splice the wires for a security camera

Frank Gates Updated April 17, 2017

Security cameras need two types of cables to operate, a power supply cable and a video cable. Wireless security cameras do not require a video cable but they do require the power supply cable. The power cable transports 12V DC, low-voltage power from the transformer, which is plugged into an 110VAC power outlet, to the camera. This cable has two 18 gauge wires, a positive wire and a negative wire, both inside a single jacket. The negative wire will be marked with a black or white stripe. The video cable is a RG-59: coaxial cable which is shielded and requires BNC connectors to protect the integrity of the video signal being carried.

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Use your knife or cable cutters to split the two insulated wires apart approximately three inches from the cut end of the cable, leaving the installation intact on both wires. You can usually pull these apart with your hands. Do this on both ends which you intend to splice together. You should now have two power cables, with two insulated wires coming out of each for a total of four wires to be spliced.

Remove half an inch of the insulation from the end of each of these four wires.

Splice these two power cables together, using wire nuts, by twisting the exposed copper ends together making sure that you twist positive from one cable to the positive from the other cable and the negative wire, or striped wire, from one cable to the negative wire, or striped wire, from the other cable. Screw a wire nut on to the joined or twisted together positive wires and a second wire nut on the twisted together negative wires. Lay the wire nuts against the cable and wrap everything with insulated electricians tape.

Splice these two power cables together, using Butt connectors, by preparing the cables just like you did for the wire nut splice, only without twisting them together. Insert the exposed copper wire from the positive conductor into one end of the butt connector and crimp that end of the connector down. Insert the other positive wire into the other end of the same butt connector and crimp it down. Do the same for the two negative wires using a second Butt connector. Wrap everything with insulated electricians tape.

Look at the cut end of the RG-59 cable and you will see four separate parts which make up this cable. In the centre is the copper centre conductor wire. Surrounding the centre conductor wire is a polyurethane white insulator. Next is the aluminium or copper braid. And finally, there is the outer jacket of the cable. As you prepare this cable for the BNC connector is important that you prepare each of these four separate parts independently of each other. The copper centre conductor must remain untouched by the braid.

Take the BNC crimping tube and hold it alongside the end of the RG 59 cable to measure your first cut. The crimping tube will have a larger diameter part and a smaller diameter part. The larger diameter part is the end of the crimping tube that you want to match against the end of the RG-59 cable.

Mark, or just eyeball, the outer jacket on the cable where the large part of the crimping tube ends and the smaller part begins. This will be about 3/8 or 1/2 inch from the end of the cable. This measurement depends on the length of the large part of the crimping tube which you have purchased with the BNC connector.

Cut and remove the outer jacket only by ringing it with a pocket knife or using cable cutters. Be very careful not to damage the aluminium braid which is right underneath the outer jacket.

Unravel the exposed aluminium braid so you can pull it away from the polyurethane insulation around the copper centre conductor.

Cut and remove the polyurethane insulation from the copper centre conductor. You can ring it with a knife or use cable cutters and it should pull free towards the cut end of the centre conductor. The cable is now ready for the connector and the cable should now have only the copper centre conductor exposed and the aluminium braid pulled back over the outer jacket.

Slide the crimp tube over the cable with the small end going on the cable first. Before you can slide the crimp tube on you must pull the aluminium braid towards the cut end of the cable so the crimp tube can go around it and slide directly onto the outer jacket of the cable.

Slide the BNC connector into place, small end first, with the copper centre conductor and the polyurethane insulation going inside of the small part of the connector and the aluminium braid and outer jacket staying on the outside of the small part of the connector. As you push the connector down into the cable it will pull the aluminium braid down inside the outer jacket at the same time. Looking inside the connector and make sure that none of the aluminium braid has inadvertently remained inside the connector and possibly touching the centre conductor. If the aluminium braid is touching the centre conductor the connection will not work.

Slide the crimping tube back up the outer jacket until it is touching the BNC connector. Use your crimping tool to now crimp the larger portion of the crimping tube and complete the compression placement of the BNC connector.

Repeat this process, placing the second BNC connector on the second piece of cable. When you have completed this you should have two pieces of video cable with a BNC connector on each piece. Use the BNC barrel connector to connect these BNC connectors together. The video cable splice is now complete.

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About the Author

Frank Gates started writing technical documents in 1980 as part of his telecommunications job. He is now a full-time technical writer. Gates has published two books, "Motorcycle Rider Basics" and "The Absolute Supervisor." He earned a technical diploma in electronic communications from the DeVry Institute of Technology.